使用Mockito有什么方法可以模拟类中的某些方法，但不能模拟其他方法吗？
例如，在这个（公认是人为设计的）Stock类中，我想模拟getPrice()和getQuantity()的返回值（如下面的测试片段所示），但我希望getValue()执行Stock类中编码的乘法
public class Stock {
private final double price;
private final int quantity;
Stock(double price, int quantity) {
this.price = price;
this.quantity = quantity;
}
public double getPrice() {
return price;
}
public int getQuantity() {
return quantity;
}
public double getValue() {
return getPrice() * getQuantity();
}
@Test
public void getValueTest() {
Stock stock = mock(Stock.class);
when(stock.getPrice()).thenReturn(100.00);
when(stock.getQuantity()).thenReturn(200);
double value = stock.getValue();
// Unfortunately the following assert fails, because the mock Stock getValue() method does not perform the Stock.getValue() calculation code.
assertEquals("Stock value not correct", 100.00*200, value, .00001);
}
要直接回答您的问题，是的，您可以模拟某些方法而不模拟其他方法。这被称为部分模拟。有关更多信息，请参阅有关部分mock的Mockito文档。
例如，您可以在测试中执行以下操作：
Stock stock = mock(Stock.class);
when(stock.getPrice()).thenReturn(100.00); // Mock implementation
when(stock.getQuantity()).thenReturn(200); // Mock implementation
when(stock.getValue()).thenCallRealMethod(); // Real implementation
在这种情况下，除非在when(..)子句中指定thenCallRealMethod()，否则每个方法实现都将被模拟。
还有一种可能性是使用间谍而不是模拟：
Stock stock = spy(Stock.class);
when(stock.getPrice()).thenReturn(100.00); // Mock implementation
when(stock.getQuantity()).thenReturn(200); // Mock implementation
// All other method call will use the real implementations
在这种情况下，所有方法实现都是真实的，除非您已经用when(..)定义了一个模拟行为。
当您在前面的示例中使用类似spy的when(Object)时，有一个重要的陷阱。实际方法将被调用（因为在运行时stock.getPrice()是在when(..)之前评估的）。如果您的方法包含不应调用的逻辑，则这可能是一个问题。你可以这样写前面的例子：
Stock stock = spy(Stock.class);
doReturn(100.00).when(stock).getPrice(); // Mock implementation
doReturn(200).when(stock).getQuantity(); // Mock implementation
// All other method call will use the real implementations
另一种可能是使用org.mockito.Mockito.CALLS_REAL_METHODS，例如：
Stock MOCK_STOCK = Mockito.mock( Stock.class, CALLS_REAL_METHODS );
这将未调试的调用委托给真实的实现。
然而，对于您的示例，我相信它仍然会失败，因为getValue()的实现依赖于quantity和price，而不是getQuantity()和getPrice()，这正是您嘲笑的。
另一种可能性是完全避免模拟：
@Test
public void getValueTest() {
Stock stock = new Stock(100.00, 200);
double value = stock.getValue();
assertEquals("Stock value not correct", 100.00*200, value, .00001);
}
mockito 中的Spy也支持对类的部分嘲讽
List list = new LinkedList();
List spy = spy(list);
//optionally, you can stub out some methods:
when(spy.size()).thenReturn(100);
//using the spy calls real methods
spy.add("one");
spy.add("two");
//size() method was stubbed - 100 is printed
System.out.println(spy.size());
查看1.10.19和2.7.22文档了解详细说明。
根据文档：
Foo mock = mock(Foo.class, CALLS_REAL_METHODS);
// this calls the real implementation of Foo.getSomething()
value = mock.getSomething();
when(mock.getSomething()).thenReturn(fakeValue);
// now fakeValue is returned
value = mock.getSomething();
根据文档，您想要的是org.mockito.Mockito.CALLS_REAL_METHODS：
/**
* Optional <code>Answer</code> to be used with {@link Mockito#mock(Class, Answer)}
* <p>
* {@link Answer} can be used to define the return values of unstubbed invocations.
* <p>
* This implementation can be helpful when working with legacy code.
* When this implementation is used, unstubbed methods will delegate to the real implementation.
* This is a way to create a partial mock object that calls real methods by default.
* <p>
* As usual you are going to read <b>the partial mock warning</b>:
* Object oriented programming is more less tackling complexity by dividing the complexity into separate, specific, SRPy objects.
* How does partial mock fit into this paradigm? Well, it just doesn't...
* Partial mock usually means that the complexity has been moved to a different method on the same object.
* In most cases, this is not the way you want to design your application.
* <p>
* However, there are rare cases when partial mocks come handy:
* dealing with code you cannot change easily (3rd party interfaces, interim refactoring of legacy code etc.)
* However, I wouldn't use partial mocks for new, test-driven & well-designed code.
* <p>
* Example:
* <pre class="code"><code class="java">
* Foo mock = mock(Foo.class, CALLS_REAL_METHODS);
*
* // this calls the real implementation of Foo.getSomething()
* value = mock.getSomething();
*
* when(mock.getSomething()).thenReturn(fakeValue);
*
* // now fakeValue is returned
* value = mock.getSomething();
* </code></pre>
*/
因此，您的代码应该看起来像：
import org.junit.Test;
import static org.mockito.Mockito.*;
import static org.junit.Assert.*;
public class StockTest {
public class Stock {
private final double price;
private final int quantity;
Stock(double price, int quantity) {
this.price = price;
this.quantity = quantity;
}
public double getPrice() {
return price;
}
public int getQuantity() {
return quantity;
}
public double getValue() {
return getPrice() * getQuantity();
}
}
@Test
public void getValueTest() {
Stock stock = mock(Stock.class, withSettings().defaultAnswer(CALLS_REAL_METHODS));
when(stock.getPrice()).thenReturn(100.00);
when(stock.getQuantity()).thenReturn(200);
double value = stock.getValue();
assertEquals("Stock value not correct", 100.00 * 200, value, .00001);
}
}
对Stock stock = mock(Stock.class);的调用调用org.mockito.Mockito.mock(Class<T>)，如下所示：
public static <T> T mock(Class<T> classToMock) {
return mock(classToMock, withSettings().defaultAnswer(RETURNS_DEFAULTS));
}
值为RETURNS_DEFAULTS的文档说明：
/**
* The default <code>Answer</code> of every mock <b>if</b> the mock was not stubbed.
* Typically it just returns some empty value.
* <p>
* {@link Answer} can be used to define the return values of unstubbed invocations.
* <p>
* This implementation first tries the global configuration.
* If there is no global configuration then it uses {@link ReturnsEmptyValues} (returns zeros, empty collections, nulls, etc.)
*/
使用Mockito的间谍方法进行部分嘲讽可能是解决问题的方法，正如上面的答案中所述。在某种程度上，我同意，对于您的具体用例，模拟DB查找可能更合适。根据我的经验，这并不总是可能的——至少在没有其他解决方案的情况下是不可能的——我会认为这是非常麻烦或至少是脆弱的。请注意，部分嘲讽不适用于Mockito的盟友版本。您至少使用了1.8.0。
我只想为最初的问题写一个简单的评论，而不是发布这个答案，但StackOverflow不允许这样做。
还有一件事：我真的无法理解，很多时候在这里被问到的问题都会被评论为"你为什么要这么做"，而至少没有试图理解这个问题。特别是当需要进行部分嘲讽时，我可以想象有很多用例会有用。这就是为什么Mockito的人提供了这种功能。这个功能当然不应该被过度使用。但是，当我们谈论无法以非常复杂的方式建立的测试用例设置时，应该使用间谍活动。